The aims of this project are (1) to understand the molecular mechanism for depression of synthesis of enzymes involved in polysaccharide synthesis that occurs in capR, capS, and capT mutants (2) to understand the molecular mechanism of control of cell division as it is specifically related to the point mutations in the E. coli K12 gene designated capR (plus). The capR mutants, besides overproducing polysaccharide synthesizing enzymes, are also sensitive to UV, x-rays and ozone, Upon UV or x-ray exposure, they form long filaments without crosswalls and these forms are nonviable. The capR plus gene specifies a protein (as determined by genetic studies) that appears to be a repressor or controls repressors that bind to many sites on the E. coli chromosome to stop synthesis of enzymes of polysaccharide synthesis. The capR plus protein may function similarly to control UV and x-ray sensitivity. We intend to isolate the capR plus protein by first obtaining the capR gene (DNA) on a tetracycline resistance plasmid DNA (10 to the 7th power daltons) using tetracycline as a selective marker and combining DNA molecules in vitro with restriction enzymes and DNA ligase. We can then amplify the capR plus protein in each cell to permit us to isolate the protein. Using genetic techniques we will also identify the postulated DNA site (the "UV operon" for structural genes) of capR plus protein action that is responsible for causing a UV and x-ray sensitive phenotype in capR (plus) mutants. Recent results indicate that the gal operon, in addition to being controlled negatively by the classic galR repressor and positively by cyclic-AMP and cyclic AMP receptor protein, is also independently regulated negatively by the capR protein. This is the most complex control system available that can readily be investigated at the molecular level and we will pursue this subject in conjunction with those described above. The capR gene also effects bacteriophage Lambda transcription and commitment to lytic growth and we are pursuing this fact with Lambda lac phages. BIBLIOGRAPHIC REFERENCE: Bacha, P., S. Hua and A. Markovitz. 1977. A gal region mutant that requires cAMP for growth on galactose in an adenyl cyclase negative (cya delta) background. Mol. Gen. Genet., in press.